1. Field of the Invention
This invention relates to an electrophotographic photosensitive member, and a process cartridge and an electrophotographic apparatus which have the electrophotographic photosensitive member.
2. Description of the Related Art
As an electrophotographic photosensitive member (hereinafter also simply “photosensitive member”), in view of advantages of low prices and high productivity, an organic electrophotographic photosensitive member has become popular, which has a support and provided thereon a photosensitive layer (organic photosensitive layer) making use of organic materials as photoconductive materials (such as a charge generating material and a charge transporting material). As the organic electrophotographic photosensitive member, in view of advantages such as a high sensitivity and a variety for material designing, an electrophotographic photosensitive member is prevalent which has a multi-layer type photosensitive layer having a charge generation layer containing a charge generating material and a charge transport layer containing a charge transporting material; the layers being superposed to form the photosensitive layer. The charge generating material may include photoconductive dyes and photoconductive pigments. The charge transporting material may include photoconductive polymers and photoconductive low-molecular weight compounds.
The electrophotographic photosensitive member is used under direct application of electrical external force and/or mechanical external force of charging, exposure, development, transfer and cleaning, and hence is required to have durability to such external force. Stated specifically, the photosensitive member is required to have durability to the scratching and wear of surface that come about because of such external force, i.e., scratch resistance and wear resistance.
In regard to improvement in the wear resistance, polycarbonate resin has hitherto widely been used as a binder resin for surface layers of electrophotographic photosensitive members. However, in recent years, it is proposed that polyarylate resin, which has a higher mechanical strength than the polycarbonate resin, is used as a binder resin for the surface layers so that electrophotographic photosensitive members can be more improved in durability (running performance) (see, e.g., Japanese Patent Application Laid-open No. H10-39521). The polyarylate resin is one of aromatic dicarboxylic acid polyester resins.
Japanese Patent Application Laid-open No. H02-127652 discloses an electrophotographic photosensitive member having as a surface layer a cured layer making use of a curable resin as a binder resin. Japanese Patent Applications Laid-open No. H05-216249 and No. H07-072640 also disclose an electrophotographic photosensitive member having as a surface layer a charge transporting cured layer formed by subjecting monomers to cure polymerization in the presence of energy of heat or light; the monomers being a binder resin monomer having a carbon-carbon double bond and a monomer having a charge transporting function and having a carbon-carbon double bond. Japanese Patent Applications Laid-open No. 2000-066424 and No. 2000-066425 further disclose an electrophotographic photosensitive member having as a surface layer a charge transporting cured layer formed by subjecting a compound to cure polymerization in the presence of energy of electron rays; the compound being a hole transporting compound having a chain-polymerizable functional group in the same molecule.
Thus, in recent years, as a technique by which the scratch resistance and wear resistance of the peripheral surfaces of organic electrophotographic photosensitive members are improved, a technique has been proposed in which the surface layers of electrophotographic photosensitive members are formed as cured layers so as to improve the mechanical strength of the surface layers.
Now, the electrophotographic photosensitive member is commonly used in an electrophotographic image forming process having, as mentioned above, a charging step, an exposure step, a developing step, a transfer step and a cleaning step. Of the electrophotographic image forming process, the cleaning step, in which transfer residual toner remaining on the electrophotographic photosensitive member after the transfer step is removed to clean the peripheral surface of the electrophotographic photosensitive member, is an important step in order to obtain sharp images. A cleaning method making use of a cleaning blade is a cleaning method operated by bringing the cleaning blade and the electrophotographic photosensitive member into friction with each other. Some fictional force between the cleaning blade and the electrophotographic photosensitive member may cause phenomena such as chattering of the cleaning blade and turn-up of the cleaning blade. Here, the chattering of the cleaning blade is a phenomenon in which the frictional resistance acting between the cleaning blade and the peripheral surface of the electrophotographic photosensitive member becomes so high as to make the cleaning blade vibrate. The turn-up of the cleaning blade is a phenomenon in which the cleaning blade comes reversed in the direction of surface movement of the electrophotographic photosensitive member.
These problems involved in the cleaning blade and electrophotographic photosensitive member show a tendency to become remarkable as the surface layer of the electrophotographic photosensitive member has a higher wear resistance to make the peripheral surface of the electrophotographic photosensitive member not more easily wear. In addition, the surface layer of the organic electrophotographic photosensitive member is commonly often formed by dip coating, and the surface of a surface layer formed by this dip coating shows a tendency to be smoother. Hence, the cleaning blade and the peripheral surface of the electrophotographic photosensitive member come into contact with each other in a larger area and the cleaning blade and the peripheral surface of the electrophotographic photosensitive member come into friction with each other in a higher resistance. Thus, the above problems show a tendency to become remarkable.
As one of methods for overcoming these problems involved in the cleaning blade and electrophotographic photosensitive member (chattering of the cleaning blade and turn-up of the cleaning blade), a method is proposed in which the surface of the electrophotographic photosensitive member is appropriately roughened.
As a method of roughening the surface of the electrophotographic photosensitive member, Japanese Patent Application Laid-open No. S53-92133 discloses a technique in which the surface roughness of the electrophotographic photosensitive member is controlled within a specific range in order to make transfer materials readily separable from the surface of the electrophotographic photosensitive member. Japanese Patent Application Laid-open No. S53-092133 also discloses a method in which drying conditions in forming a surface layer is controlled to roughen the surface of the electrophotographic photosensitive member in orange peel. Japanese Patent Application Laid-open No. S52-026226 discloses a technique in which the surface layer is incorporated with particles to roughen the surface of the electrophotographic photosensitive member. Japanese Patent Application Laid-open No. S57-094772 discloses a technique in which the surface of a surface layer is polished with a wire brush made of a metal to roughen the surface of the electrophotographic photosensitive member. Japanese Patent Application Laid-open No. H01-99060 discloses a technique in which a specific cleaning device and a toner are used to roughen the surface of an organic electrophotographic photosensitive member. According to this Japanese Patent Application Laid-open No. H01-099060, it is described that the problems of turn-up of the cleaning blade and chipping of edges thereof can be solved which may come into question when used in an electrophotographic apparatus having a certain higher process speed.
Japanese Patent Application Laid-open No. H02-139566 discloses a technique in which the surface of a surface layer is polished with a filmy abrasive to roughen the surface of the electrophotographic photosensitive member. Japanese Patent Application Laid-open No. H02-150850 discloses a technique in which blasting is carried out to roughen the surface of the electrophotographic photosensitive member. This, however, has no specific disclosure as to details of surface profile of the electrophotographic photosensitive member surface-roughed by such a method. International Publication No. WO2005/93518A1 discloses a technique in which the above blasting is carried out to roughen the peripheral surface of the electrophotographic photosensitive member, and discloses an electrophotographic photosensitive member having a stated dimple profile. It is described therein that improvements have been achieved in regard to smeared images tending to come about in a high-temperature and high-humidity environment and transfer performance of toner. Japanese Patent Application Laid-open No. 2001-066814 also discloses a technique in which the surface of the electrophotographic photosensitive member is processed by compression forming by means of a stamper having unevenness in the form of wells.